European Patent EP 1 455 374 B1 discloses a low-voltage isolating switch which has at least one moving contact, which can be connected to and disconnected from a corresponding fixed contact, as well as a positive-opening device. The latter has a moving element which is associated with the moving contact, a first drive train which is operatively connected to the moving contact and to an actuating device, as well as a second drive train, which is connected to the moving element and to the first drive train. A first lever is associated with the first drive train, and a second lever is associated with the second drive train. The first and second levers interact with one another during the opening operation. Both levers are provided with blocking devices for the situation in which the contacts are welded to one another.